Technical Abstract:
Disease significantly reduces grain yield. It is not known if model plant systems will provide an adequate framework for understanding resistance mechanisms in cereals. For this reason we are developing tools for the functional analysis of a broad-range of disease resistance pathways in barley and wheat. Given the relative lack of mutations affecting disease resistance in cereals we have chosen an approach based on the hypothesis that the majority of genes playing critical roles in mechanisms of resistance will be differentially expressed during resistance and susceptibility. To this end we have characterized the significant changes in gene expression in a range of compatible and incompatible interactions, including the fungi Fusarium graminearum and Mycosphaerella graminicola, Barley Yellow Dwarf virus and Hessian fly. We utilized an open-architecture expression profiling technology, GeneCalling, which enables characterization of differentially expressed transcripts without requirement of prior knowledge of genome sequence. GeneCalling detected >11,000 cDNA fragments whose expression changes differed by at least 1.5 fold between treatments. These sequences were used to create microarrays that are being employed in extensive timecourse analyses of compatible and incompatible interactions. These analyses are yielding prioritized sequences whose function in resistance will be tested in a virus-induced gene silencing assay. The assay utilizes Barley Stripe Mosaic virus vectors to suppress expression of chosen genes in resistant genotypes, which are then challenged with avirulent pathogens. Conversion of an incompatible interaction to compatible will be an initial indication of the requirement for a gene in resistance.